The goal of this investigation is to test the hypothesis that circulating estrogen and striatal dopamine (DA) receptor availability interact with one another to influence self-control. Specifically, we predict that increased circulating estrogen wil decrease DA D2-type receptor availability, and this decrease in DA receptor availability will decrease performance on two self-control tasks, the Stop-Signal Task and an emotion regulation task. Self-control tasks have previously been shown to be influenced by DA signaling in both animals and humans, and a smaller number of studies have shown a relationship between estrogen levels and performance on self-control tasks. Therefore, we will test our hypothesis first by measuring DA D2 receptor availability in the brain using Positron Emission Tomography (PET) imaging and measuring estrogen levels in blood serum (Aim 1). Next, participants will complete two self-control tasks that share a common neural substrate: the Stop Signal Task, a measurement of impulsive action (Aim 2) and cognitive reappraisal of emotions (Aim 3). We will enter the results of each behavioral experiment into a statistical model with serum estrogen levels and striatal DA D2 receptor availability measured by BPND to test our hypothesis that circulating estrogen decreases DA D2 receptor availability, and this decrease in receptor availability decreases self-control. If the data support this hypothesis, our findings wil suggest that hormone state is an important factor to consider in experiments that involve self-control tasks and, more importantly, when attempting to modify behaviors that depend on self-control, in particular, addiction.